(1) Field of the Invention
This invention relates to trawling apparatus. In particular the invention relates to improvements in otterboards, sleds and mid-water boards for trawling apparatus.
(2) Prior Art
Conventional otterboards and sleds are worked to depths of 1000 meters. The major problem with the conventional otterboards is maintaining the boards on the ocean floor and so it is not uncommon to use otterboards weighing upto 650 kg. and sleds weighing upto 200 kg., both incorporating large, heavy steel shoes.
These known otterboards and sleds are difficult to handle and can only be towed at speeds below e.g. 2.2 knots or they tend to be pulled up from the ocean floor.
Many solutions to overcome the problems with known otterboards have been proposed and are disclosed in DE No. 205670; U.S. Pat. No. 2767504; GB No. 21279 (1897); GB No. 224128; GB No. 207177; FR No. 1189592 and FR No. 1220709.
None of the cited otterboards have proved successful and so trawler men have reverted to relying on weight to maintain the otterboards on the ocean floor.